George i



' UNITED STATES PATENT OFFICE.

GEORGE R. CORNWALL, ()F PORT (JIIESTEIL'NEW YORK, LXSSIGXOl-l', ll'Y MESNE ASSIGNMENTS, TO THE CORNWALL PRIN'IING PRESS COM- PAN-Y, or NEW YORK, K. Y.

PROCESS O F PREPARING ALUMINIUM PLATES FOR SURFACE PRINTING.

SPECIFICATION forming part of Letters Patent No. 590,966, dated October 5, 1897.

Application filed July 9, 1896. Serial No. 598,3DQ. (Specimens) To allwhom it may concern.-

Be it known that I, GEORGE R. CORNWALL, a citizen of the United States, residing at Port Chester, county of lVestchest-er, State the subject of this invention is to remove these impurities that are an impediment or drawback and also to render the plate more porous and sensitive to the design.

The first step of my process is, by mechanical or chemical action, to remove the outer shell or skin of the metal usually formed in rolling from the ingot and'also to get down plate with water.

'belowany surface scratches or blemishes on the metal and present a true even surface for the design. The next stepaft-er I have removed the outer shell is to treat the plate with an alkaline solution (preferably caustic. potash) of strength sniii ient to dissolve any greasy material that may be on the surface or in the metal within reach of the alkali. The next step is to wash the alkalifrom the The next step is .to dip the plate in a bath of acid for the purpose of 'am1xtuge 9j n@j c and hydrofluoric acid,

removing further im purities,preferably using ("which removes cerFiifi surfaced fit or F1]- purity that the potash does not reach, also d ssl fi Us. ilic n; endccnncuendihei mhi .11am? mete eithe m y have enien'rrl intothlejlja' te in the operatiodof rolling the plate, and also any earthy material that has been incorporated in the plate either in the prod notion of the iugdt or the subsequent production of. the platefrom the ingot-. Then the acid is removed by washing in coldivater. Any remaining trace of acid is then neutralized by dipping the plate in a neutralizing solution and the plate-washed again.

More-in detail, my process is as follows: I 50 take, say,a sheet of aluminium of commerce which has on it and in it not only the ordinary commercial impurities, scratches, and blemishes, but the shell or skin which is caused by the rolling of the plate. in g has compacted the surface particles more densely than the interior. I first remove the said blemishes, scratches, and skin by buifing or rubbing down the surface, using for this in" ose means which are ada ted to the roduction of the desired grain or-surfaco finish, according to the particular work towhich the plate is to be applied. For'example, for a plate whigh is intended for stipple or line or brush work I use a buifing or grinding disk 6 having a felt or flannel faceoand as an abradant I preferably use powdered pumice-stone slightly moistened, while' for producing a plate which is intended for crayon-or grained work I produce the desired surface by sub- ,iecti ng the plate to the abrading action of wet powdered grit of some kind rolled ovcr the surface of the plate by small quartz pebbles or marbles, the size of which is varied accord ing to the size or character of grain desireclsqs [neither c'ase it is necessary and essential to my process that the abrading action should be carried on to a sufficient extent to entirely remove the on ter com pressed skin independent of the dulling, graining, or ronghening of the surface. The point at which this result is'accomplished can only be determined by actual enperiencehaf s, by taking impressions wi lLh the plates andascertaining whether the design remains clear after a number ofimpressions If itfdoes not do so even when the chemical cleaning process hereinafier described has been thoroughly effected, it indicates that a deeperabrasion is necessary. On

further cutting away of the skin to a certain extent it will be found that a design can be produced thereon which will remain permanently clear, and yet the grain or degree of roughness of the plates may be the same as in the first case, when an imperfect result was 5 obtained, the difierence in effect being due to the fact that in the second case when the skin has been completely removed there will The roll- 55 insi nznsls p ticles Silt-h as ppe or is then removed from the acid and very thorv plate is washed in clean water, and upon drying the plate is ready for the design.

.45 desired.- -In particular I may substitute for' hydrochloric or a small proportion of sulfuric washed in water to remove any alkali that is aduem anmrnmtmumm -ken action be exposed toreceive the design a sutlace of 1 soft porous aluminium which has peculiar homing and absorbent qualities. I then subject the plate to a bath in an alkaline so'lution, preferably caustic pot-ash. 'lhe'strengh of the solution depends on whether the solution is used hot or cold. Ordinaiilyata temperature of the solu t-ion may be ten pounds of caustic soda to twenty gallons of water. The plate m net. not be left in long enough. to blister it and the length of time it should be left in depends on the strength of the solution. When the plate has becom'ect peculiar slat-y black, which will he readily recognized by any one accustomed to the operation, the treatment has proceeded far enough. The plate is then removed from the solution and upon its surface. Next V solution consistingof ahont-twentyrper-eeugennatednitriensisletsnmnnis and eight? per centum of water tg h'mlnis upon the plateisligtl-ilced'. The quantity necessary for this is about one to two ,er cent. 0 h \dLQ.flllOlfiC 3tQ lf1. v This act at any surtlace dirtiir impurity which may have remaified aft-eFThFalkaiine treatment, any

iron, and an fiiiitfB i-dirt that may hayebeep pre 'edi'nto t e Frietal byth'c rolls, also any -Emeritus nandsiliq As the plate lEEfih the bath a is wiped uiitil the dark surface is entirely remored .and the plate has a uniform,brilliant, silvery aspect. The plate oughly washed in water, preferably using hot water. Any acid remining on the plate is neutralized by then washing the plate in a solution of alum, lime-water, or any other suit-able neutralizing material. Then the The above-given ingredients and proportions may be varied according to the result the hydrofluoric acid a small propcrt-ion of acid, and for the caustic potash caustic soda or other alkaline material. Preferably the reagents used are those first given above.

the open-grained interior of the plate ex-' posed-to form the printing-surface, substantially as set forth.

2. The process of preparing aluminium plates for surface printing which consists in first removing the outer compressed skin or surface, then subjecting the plate to the action of a caustic alkaline bath and subsequently to an acid-bath, and removing all resulting salts frm the surfaceof the plate, substantially as set forth.

3. .The process of preparing aluminium surface-printing plates consisting in first abradim: the surface to remove the hard compressed shell and at the same time give the plate the desired finish, then treating the plate in an alkaline and then in an acid bath to remove the impurities, substantially as set forth.

4. The process ofpreparing aluminium surface-printing plates consisting in first removing the hard compressed shell or skin of the plate and giving it the desired finish and then chemically dissolving out the impurities without impairing the surface finish, substantially as set forth. v

- 5. The process of preparing aluminium surface-printing plates which consists in exposingthe plate in a-ecaustic alkaline bath, and subsequently in a bath containing nitric acid and a small proportion of hydrofluoric acid,

and removing the resulting salts from the surface of the plates, so as to leave the latter exposed to form the printing-surface.

6. The process of opening up the grain and purification of aluminium surface-printing plates, consisting in exposing the same in a 

